Broadcast antenna



Nov. 23, 1948. P. s. CARTER BROADCAST ANTENNA Original Filed Dec.

Reissued Nov. 23, 1948 BROADCAST ANTENNA Philip S. Carter, Rocky Point,N. Y., assignor to Radio Corporation of America, a corporation ofDelaware Original No. 2,403,909, dated July IG, 1541:, Serial No.422,356, December 10, 1941.

Application for reissue September 8, 1948, Serial No. 48,306

19 Claims. (01. 250-33.63)

The present invention relates to antennae for radiating verticallypolarized short wave energy.

An object of the present invention is the provision of a broad bandantenna for vertically polarized waves which does not use a verticallyprojecting radiating conductor.

Another object is the provision of a simple, easily constructed radiatorfor vertically polarized waves which is capable of operating Withoutdiscrimination over a wide band of frequencies.

A further object is the provision of an antenna which may be arrangedflush with the surface of a conducting ground sheet such as a fiatmetallic roof of a. building.

Still a further object is the provision of an antenna for verticallypolarized waves in which it is not required that any portion thereofproject above the surface of the ground.

The foregoing objects, and others which may appear from the followingdetailed description, are attained by expanding the electric fieldwithin a concentric transmission line connected to a high frequencyenergy source by expanding the outer conductor of the line and bycontracting the inner conductor to a point until propagation takes placewithout the inner conductor. The field is then further expanded byflaring the outer conductor until the field may be propagated smoothlyaway from the system in a plane normal to the axis of the transmissionline and sub stantially uniformly in all directions in that plane.Conversely, the antenna is operative for reception of radiant energy,the tapered portions acting to successively contract the field until itmay be carried along the transmission line to a receiver.

The present invention will be more completely understood by reference tothe following detailed description which is accompanied by a drawing inwhich Figure 1 illustrates an embodiment of the present invention andFigure 2 illustrates a modification thereof. In Fig. l I have shown aconcentric cable transmission line TL composed of an outer shellconductor I and an inner central conductor 2. line is connected to asource. of high frequency energy (not shown) and the other end which isto also serve as a radiator, is preferably vertically disposed. This endof the transmission line is divided into a plurality of consecutivezones in each of which different operations are performed on the wave tobe radiated. In the first zone, identified by reference numeral 3, theouter conductor is expanded in diameter until its diameter d is greaterthan that value for which One end of the transmission where J0 is thezero order Bessel'function of the first kind, that is of constantdiameter, or it may continue to expand. Finally, in zone 5, the outerconductor is further expanded and flared like a trumpet, at

last curving around back on itself, as indicated i at 6. The changingdimensions cause the electric field of the wave in the concentric lineto gradually expand first in zone 3 by expansion of the outer conductorand then in zone 4 by contraction of the inner conductor until, in zone5, propagation takes place without the inner 00nductor. The electricfield then is expanded further in zone 5 and is propagated away fromthe" system horizontally as indicated by the electric lines of force E.No propagation takes place vertically.

The foregoing description has been predicated on the assumption that theend of the transmission line is vertically disposed. Of course, ifdesired, the system. may be adapted to radiate: horizontally polarizedenergy by disposing the upper face of the expanded portion of thetransmission line vertically, instead of horizontally, as shown.

While the extreme end portion of the outer con- I ductor has been shownas curving around back onv itself in Fig. 1, it is within the scope ofthe present invention to simply extend the flared poran airport, forexample, where any projections would constitute a hazard to planeslanding and taking off. In this form of construction it is preferredthat the open flared end of the outer conductor be closed in with asthin as possible a sheet of dielectric material such as that indicatedby reference character I2 in order to provide protection against theelements and to present a smooth overall surface. The closure should bethin in order not to cause excessive losses or distortion of the field.Furthermore, while only a single radiator element has been shown anddescribed, it should beclearly understood that a plurality of elementsmay be so disposed as to.

obtain directivity in the horizontal plane by arranging said elements sothat energy from the elements is in a phase additive relationship in thedesired direction.

While I have shown and particularly described several embodiments of myinvention, it is to be distinctly understood that my invention is notlimited thereto but that modifications within the scope of my inventionmay be 'made.

I claim:

1. A system for radiating or receiving electromagnetic waves withsubstantially uniform intensity in all directions normal to a given axiscomprising a concentric transmission line lying along said axis andhaving an outer shell and an inner conductor connected to a wave energy1 transducer, said outer shell being flared out in a trumpet-likeformation, said inner conductor being tapered to a point and entirelycontained within said flared outer shell.

2. A system for radiating or receiving electromagnetic waves comprisinga, concentric transmission line having an outer shell and an innerconductor connected to a wave energy transducer, said outer shell beingflared out in a trumpet-like formation, said inner conductor beingtapered to a point and. entirely contained within said flared outershell, the longitudinal axis of said line being vertically disposedwhereby said system is uniformly responsive in the horizontal plane tovertically polarized waves.

3. A system for radiating or receiving electromagnetic waves comprisinga' concentric transmission line having an outer shell and an innerconductor connected to a wave energy transducer, said inner conductorbeing tapered to a point and entirely contained within said outer shellsaid outer shell being so flared out in a trumpet-like formation withthe outer end of the shell curvedv back on itself that the field withinsaid shell is smoothly converted to a field extending substantiallyuniformly in all directions normal to the axis of the flared portion ofthe said shell.

4. A system for radiating or receiving electromagnetic waves comprisinga concentric transmission line having an outer shell and an innerconductor connected to a wave energy transducer,

said outer shell being flared out in a trumpet-like formation with theouter end of said shell curved back on itself, said inner conductorbeing tapered to a point and entirely contained within said flared outershell, the longitudinal axis of said line being vertically disposedwhereby said system is uniformly responsive in the horizontal plane tovertically polarized waves.

5. A system for radiating electromagnetic waves comprising a concentrictransmission line having its longitudinal axis vertically disposed andsaid line including an outer shell and an inner conductor connected toa. wave energy source, said inner conductor being tapered to a pointentirely within said outer shell, said outer shell being so flared, outin a trumpet-like forma tion that vertically polarized energy isradiated uniformly in all directions in the horizontal plane.

6. A system for radiating electomagnetic waves comprising a, concentrictransmission line having an outer shell and an inner conductor connectedto a wave energy source, said outer shell being flared out in atrumpet-like formation with the outer-end of said shell curved back onitself, said inner conductor being tapered to a point within said flaredouter shell, the flare of said outer shell being so proportional thatthe field within said shell is smoothly converted to a' field extending4 substantially uniformly in all directions normal to the axis of theflared portion of said shell.

7. A system for radiating electromagnetic waves comprising a concentrictransmission line having an outer shell and an inner conductor connectedto a wave energy source, said outer shell being flared out in atrumpet-like formation with the outer end of said shell curved back onitself, said inner conductor being tapered to a point and entirelycontained within said outer shell, the longitudinal axis of said linebeing vertically disposed whereby vertically polarized. energy isradiated uniformly in all directions in the horizontal plane.

8. In a radiant energy system, a concentric transmission line having anouter shell and an inner conductor, said outer shell being smoothlyexpanded in its transverse dimension along a portion of the length ofsaid line until the propagation of the field within said shell may'takeplace Without said inner conductor, said inner conductor being taperedtoa point, said outer conductor thereafter being so flared out that saidfield is freed from said system and is propagated in all directionsnormal to the length of said line.

9. In a radiant energy system, a concentric transmission linehaving anouter shell and an inner conductor, said outer shell being smoothlyexpanded in its transverse dimension along a portion of the length ofsaid line until the propaga tion of the field within said shell may takeplace without said inner conductor, said inner conductor being taperedto a point, said outer conductor thereafter being flared out until saidfield is free from said system, the flare of said shell being continuedso that the end of said shell is curved back v on itself.

10. In a radiant energy system, a concentric transmission line having anouter shell and an inner conductor, said outer shell being smoothlyexpanded in its transverse dimension along a portion of the lengthofsaid line until the propaga- .tion of the field within said shell maytake place without said inner conductor, said inner conduc-.

tor being tapered to a point along the next adjacent length of saidline, said outer conductor thereafter along the length of said linebeing flared out until said field is free from said system.

11. In a radiant energy system, a concentric transmission line havinganouter shell and an inner conductor, said outer shell being smoothlyexpanded in its transverse dimension along a por- .tion of the length ofsaid line until the propagation of the field within said shell may takeplace without said inner conductor, said inner conductor being taperedto a point along the next adjacent length of said line, said outerconductor thereafter along the length of said line being flared outuntil said field is free from said system,

the flare of said shell being continued so that the end of said shell iscurved back on itself.

12. In a radiant energy system, a concentric transmission line having anouter shell and an inner conductor, said outer shell being smoothlyexpanded in its diameter d along a portion of the length of said lineuntil said diameter is greater than that value for which Where Jo is thezero order Bessel function of the first kind, that is,v

where x is the operating wavelength whereby propagation of the fieldwithin said shell may take place without said inner conductor, saidinner conductor being tapered to a point along the next adjacent lengthof said line and said outer conductor thereafter along the length ofsaid line being flared out until said field is free from said system.

13. In a radiant energy system, a concentric transmission line having anouter shell and an inner conductor, said outer shell being smoothlyexpanded in its diameter d along a portion of the length of said lineuntil said diameter is greater than that value for which where Jo is thezero order Bessel function of the first kind, that is,

where A is the operating wavelength, whereby propagation of the fieldwithin said shell may take place without said inner conductor, saidinner conductor being tapered to a point along the next adjacent lengthof said line and said outer conductor thereafter along the length ofsaid line being flared out until said field is free from said system,the flare of said shell being continued so that the end of said shell iscurved back on itself.

14. A radiant energy transmission system including a hollow wave guidemember having a transverse dimension such that propagation of theradiant energy field within said guide may take place without thepresence of an inner conductor, said member being flared at one end tosuch an extent that the field within said guide is free from saidsystem, and said flare being further continued so that the end of saidguide is curved back on itself.

15. A radiant energy transmission system including a hollow wave guidemember having a diameter d greater than that value for which where Jo isthe zero order Bessel function of the first kind, that is,

where A is the operating wavelength, said member being so flared out atone end that the field within said guide is freed from said system andis propagated in all directions normal to the length of said member.

16. A radiant energy transmission system including a hollow wave guidemember having a diameter d greater than that value for which where Jo isthe zero order Bessel function of the first kind, that is,

Number 6 where A is the operating wavelength, said member being flaredout at one end until the field within said guide is free from saidsystem, the flare of said guide being so continued that the end thereofis curved back on itself.

17. A system for radiating electromagnetic waves comprising a concentrictransmission line having an outer shell and an inner conductor connectedto a wave energy source, said inner conductor being tapered to a pointentirely within said outer shell, said outer shell being flared out in atrumpet-like formation so that the field within said shell is smoothlyconverted to a field extending substantially uniformly in all directionsnormal to the axis of the flared portion of said shell.

18. In a radiant energy system, a concentric transmission line having anouter shell and an inner conductor, said outer shell being smoothlyexpanded in its transverse dimension along a portion of the length ofsaid line until the propagation of the field Within said shell may takeplace without said inner conductor, said inner conductor being taperedto a point, said outer conductor thereafter being so flared out thatsaid field is freed from said system, said outer conductor mergingsmoothly into a plane conductive sheet normal to the axis of said line.

19. A radiant energy transmission system including a hollow wave guidemember having a diameter 11 greater than that value for which where Jois the zero order Bessel function of the first kind, that is,

Where A is the operating wavelength, said member being so flared out atone end that the field within said guide is freed from said system, theflare of said member merging smoothly into a plane conductive sheetnormal to the axis of said guide member.

PHILIP S. CARTER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date Dallenbach May '7, 1940 Wolfi July 16,1940 Schelkunoff Mar. 18, 1941 Southworth Feb. 11, 1941 Lindenblad Apr.29, 1941 Peterson Mar. 10, 1942 Von Baeyer Aug. 11, 1942 FOREIGN PATENTSCountry Date Great Britain Nov. 1, 1938 Great Britain Nov. 23, 1938Number

